Generally in internal combustion engines, in a four-cylinder diesel engine for example, vertical and horizontal first-order unbalanced moments arise during the driving thereof. Such first-order unbalanced moments have been conventionally balanced by fitting fly-wheels with counterweights placed thereon on the front and rear ends of a shaft of a diesel engine, and allowing the fly-wheels to rotate with the rotation of the shaft.
In the above-mentioned case, however, the sum of the vertical first-order unbalanced moment and the horizontal first-order unbalanced moment is maintained at a constant relationship, and when one of the first-order unbalanced moment is reduced by the compensation thereof, the other first-order unbalanced moment is increased thereby, causing an inconvenience that both vertical and horizontal moments may not be simultaneously balanced.
While chain-balancers or electric balancers have been conventionally used to balance the vertical second-order unbalanced moment and to decrease the vibrating force of one direction, namely the vertical direction, if chain-balancers or electric balancers are applied for balancing vertical and horizontal first-order unbalanced moments, the counterweights or the balancers become too big to be loaded on diesel engines of vessels and so on.